Calories: Basics
Calories is a word many of us are familiar with. With rates of obesity rising, as well as increased awareness of health complications associated with excess fat, we frequently hear of calories being counted and cut. Despite how often the word “calories” is thrown around, it is often misunderstood, and has garnered a bad reputation. It is frequently seen as the enemy that is the main cause for weight gain.
While excess calories lead to weight gain, they are an essential component to our health. Our bodies need energy in order to survive, and calories are a means of measuring the amount of energy we are putting into our body through food and drink and the amount we are expending through metabolic processes and physical activity.
What are calories?
There are various forms of energy, such as light energy, heat (thermal) energy, and mechanical energy. A calorie represents a unit of heat content or energy. A small calorie is defined as the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.
A large calorie, also called kilocalories (kcals), dietary calories, nutritional calories, and Calories with a capital “C,” is defined as the amount of energy required to raise one kilogram of water by one degree Celsius. 1 large calorie equals 1,000 small calories. Anything that contains energy has calories, including coal, gasoline, and food.
The term “calories” is often used interchangeably, whether it is a small or large calorie. This can make it confusing since calories in food, also known as “food calories,” are actually kilocalories. Similarly, calories listed in fitness charts indicate kilocalories as well.
While calories is a commonly used unit of measure for energy in North America on food labels, it is standard practice in other regions, including the European Union and Australia, to use joules. A small calorie equals 4.184 joules, and a food calorie contains 4184 joules.
Food calories refers to the amount of potential energy that food possesses. Different foods provide different amounts of calories, but they can be broken down into three main components: macronutrients fat, carbohydrates, and protein. Alcohol also contains calories, but it is not considered a nutrient because the body doesn’t need it.
Fat contains the highest concentration of calories, with 9 calories per gram of pure fat. Carbohydrates contain 4 calories per gram of pure carbohydrate; protein contains 4 calories per gram of pure protein; and alcohol contains 7 calories per gram of pure alcohol.
Another way of looking at it is that 1 gram of fat releases 9 calories of energy; 1 gram of carbohydrates and protein releases 4 calories of energy each; and 1 gram of alcohol releases 7 calories of energy. By knowing how many carbohydrates, fats, and proteins are in a food, you can determine how many calories, or energy, it contains.
The body “burns” calories in food through metabolic processes, in which they eventually release their stored energy. Metabolism refers to all the chemical processes that occur within a living organism, resulting in the breakdown of molecules to obtain energy and the synthesis of compounds needed by cells.
Carbohydrates are broken down into glucose and other sugars; fats are broken down into glycerol and fatty acids; and proteins are broken down into amino acids. These molecules are either absorbed into cells for immediate use or their stored energy is released.
Empty calories
Empty calories, also known as discretionary calories, are calories that supply little to no nutritional value. Main sources of empty calories include solid fats (fats that are solid at room temperature) and added sugars. These fats mainly consist of animal fats and are found in ribs, bacon, hot dogs, sausages, and cheese.
The most common types of added sugars are sucrose and high-fructose corn syrup. Foods with added sugars include fruit drinks, sports drinks, energy drinks, and sodas. Foods that contain both solid fats and added sugars include ice cream, donuts, pastries, and cakes. Solid fats and added sugars are commonly added during industrial food processes.
How many calories do we need?
Your body requires a certain amount of calories for everyday activity, and basic body functions.
How many calories a person needs to consume per day varies depending on the age, sex, weight, and muscle mass of the individual. Muscle mass burns more calories than body fat and increases the daily calorie requirement of the body.
Health officials around the world also have a hard time finding an ideal amount of calories for an individual. A good general guideline is 2000 calories per day for a middle-age moderately active female, and 2400 to 2600 calories per day for a middle-age moderately active male.
There are various methods of calculating your daily caloric requirements. The total number of calories your body needs each day depends on your BMR, AMR or activity level, and the thermic effect of food.
Basal metabolic rate (BMR)
The amount of energy your body needs to function at rest to keep your heart beating, lungs breathing, and body temperature stabilized is known as the basal metabolic rate (BMR). In general, an adult female body needs at least 1000 to 1400 calories a day to have enough energy to fuel key organs and metabolic processes, and an adult male needs at least 1400 to 1600 calories. Men tend to have a higher BMR than women.
Active metabolic rate (AMR)
Then, your body requires more calories on top of that in order to move around and perform physical activities such as making the bed, lifting, bending, walking around, and cooking. The calories you burn during physical activity is known as your active metabolic rate (AMR). This extra energy to live your day typically amounts to around 400 to 600 calories per day. If you exercise daily or do sports, then additional calories are needed.
Calculating BMR (basal metabolic rate)
There are different equations you can use to calculate (or estimate) your BMR, each with their own strengths and weaknesses. These include the Harris-Benedict formula (HB method) and Katch and McArdle (KA) method.
The Harris-Benedict formula consists of the following equations for an adult:
Male: 66 + (6.23 x body weight in lbs.) + (12.9 x height in inches) – (6.8 x age in years)
Female: 655 + (4.35 x weight in lbs.) + (4.7 x height in inches) – (4.7 x age in years)
This formula isn’t always correct and it does not take into consideration body composition (amount of body fat or lean muscle mass), but it can provide a good starting point.
The Katch and McArdle method does take into account body composition, but it relies on your body fat measurement. Your body fat measurement may not be accurate depending on what method you use to measure it.
The formula for an adult is:
BMR (Men + Women) = 370 + (21.6 x Lean Mass in kg)
Lean Mass = weight in kg – (weight in kg x body fat %)
Or BMR = 370 + (9.79759519 x Lean Mass in pounds)
These are two common methods for measuring BMR, but there are many others available. You can also use a metabolic analyzer. This is a device that you breathe into that measures the amount of oxygen you consume at rest, and then uses that measurement to calculate the calories burned during a 24 hour period. This device can indicate whether you have a slow metabolism (though having an abnormally slow metabolism isn’t as common in overweight or obese people as many believe), but can be expensive, even if you choose to pay for a test at a nutritional practice or hospital.
Calculating AMR (active metabolic rate)
Once you calculate your BMR, you can then determine your AMR by multiplying your BMR by a number representing your activity level.
Sedentary (little or no exercise): AMR = BMR x 1.2
Lightly active (light exercise/work 1-3 days per week): AMR = BMR x 1.375
Moderately active (moderate exercise/work 3-5 days per week): AMR = BMR x 1.55
Very active (hard exercise/sports and physical job 6-7 days a week): AMR = BMR x 1.725
Extra active (very hard exercise/sports and physical job 6-7 days a week): AMR = BMR x 1.9
Thermic effect of food
The thermic effect of food is the increase in metabolic rate (energy expenditure) needed for digestion. It accounts for 5 to 10 percent of your body’s daily energy requirements, and can be estimated by multiplying the total number of calories you consume in a day by 10%, or 0.10. After calculating these individual numbers, you can then add them together for an estimate of your daily caloric requirements.
If you don’t want to do the calculations yourself, there are websites that can do it for you. You just need to put in your height, weight, sex, and age. There are also charts available online that provide a general reference.
Regardless of the method you choose, you’ll need to recalculate your daily calorie needs as your weight and age changes. Your daily calorie requirements can fluctuate and it can be difficult to get an accurate amount. It can be influenced by environmental temperature and increased core body temperature. However, a good measure of whether you are consuming too much, too little, or the right amount of calories is through your weight.
Caloric balance
You want to aim for caloric balance in your diet and lifestyle. Caloric balance is when, over time, the number of calories consumed matches the number of calories you burn through metabolism and physical activity – energy intake equals energy expenditure – and you maintain body weight.
Calorie excess, also known as calorie surplus, occurs when the calories you consume exceeds your daily calorie requirements. This excess energy is stored as fat and glycogen (the storage form of carbohydrates in the human body).
Adipose tissue is the body’s most abundant and concentrated source of stored energy. As it begins to accumulate, excess weight is gained, which can lead to obesity and increased risk of cancer, heart disease, diabetes, and other metabolic disorders. It is common for people to consume far too many calories, particularly empty calories.
Many restaurants and other fast food places tend to serve portion sizes that exceed calorie recommendations for a single meal, and food manufacturers like to round down when listing total calories, so it is very easy to be unaware of the calories we are consuming, and then eat too much.
A caloric deficit occurs when you burn more calories than you consume, causing the body to release stored energy to make up for it and leading to a loss of body mass. If you are trying to lose weight, then you want to create a calorie deficit.
You can do this by reducing the amount of calories you consume each day, increasing the amount of calories you require each day by increasing your activity level, or both. 3500 calories is stored as 1 pound of fat, which means that if you use, or burn, 3500 more calories than you consume, your body will convert 1 pound of its stored fat into energy to make up for the deficit (1).
One day of fasting or overindulging does not cause instant weight gain or weight loss. You need to consume excess calories, or decrease calories each day in order to lose the weight. To lose 1 to 2 pounds per week (a good rate for a healthy, steady weight loss) you would need to reduce calorie intake by 500 calories per day.
The best way to reduce calorie intake is not to simply reduce the amount of calories you consume, but to also incorporate exercise. For example, instead of reducing 500 calories in food alone, you can reduce 250 calories from food intake, and then burn another 250 calories through physical activity. Exercise also helps increase muscle mass, which can then increase your BMR.
What are the best source of calories?
If weight is your only concern, then the source of calories would make no difference. A carbohydrate calorie is no different from a fat calorie in that they are both units of energy. If you restrict calories, regardless of where they come from, then you will lose weight. If you consume extra calories, even if they aren’t fat calories, you will still gain weight. However, where nutrition and overall health is concerned, then the source of the calories is vitally important.
Carbohydrates are broken down into glucose, your body’s main energy source. Protein contains amino acids and is used to build and repair tissues; and fats help absorb fat soluble vitamins, provide reserve energy storage, form cellular structure, and form a protective cushion and insulation around vital organs.
Carbohydrates and protein are generally considered healthier options for calories, and it is often recommended to limit fats, but it depends on the source of these nutrients, and your current health.
Avocados and cheese are both high in fat, but avocados are high in health-promoting monounsaturated fat, while cheese is high in saturated fats. High amounts of saturated fats have been shown to raise cholesterol, and has been linked with high blood pressure and insulin resistance. Instead of avoiding all fats, it is better to replace them with a healthier alternative. We need a certain level of good fats in our diet to promote optimal health.
The sources of carbohydrates and protein are equally important. We can choose to consume the empty calories found in store-bought cookies, or we can choose to eat nutrient-filled fruits instead. Animal foods, such as beef and poultry, may be high in protein, but they contain no fibre, little water, and require an increase in insulin release in order to be digested. Frequent increased insulin secretion has been linked with insulin resistance. People with diabetes or who are at risk of developing it might find it beneficial to limit calories from carbohydrates, particularly refined carbohydrates.
Often when people are trying to lose weight and “cut down” on calories, they simply consume smaller quantities of the same unhealthy foods they may be eating. This type of calorie restriction is unhealthy. It cuts out essential nutrients, leads to less food volume, less stomach stretch, and increased feelings of hunger. It can also cause your metabolism to slow down to compensate. Your stomach needs to stretch enough during each meal to signal satiety (fullness).
High calorie foods, such as refined sugars and animal foods can contain no fibre and little water, and processed foods may also have fibre and water removed. This means less stomach stretch, and less fullness.
Nutrient-dense foods, particularly whole, plant based foods, provide that necessary bulk to your diet due to their water and fibre content.
Calorie-dense foods
High calorie or calorie dense foods contain a high amount of calories relative to serving size, but, unlike empty calories, can contain nutrients.
Avocados, quinoa, nuts, olive oil, dried fruits, and moderate amounts of dark chocolate are all high calorie foods, but also contain essential nutrients. Pizza and cookies are also high calorie foods. Whether these calories are empty calories depends on whether the food is processed and the ingredients used.
Nutrient-dense foods
Nutrient dense foods are high in nutrients, but have a low amount of calories relative to serving size. They provide more nutrients than calories, while empty calorie foods supply more calories than nutrients.
Nutrient dense foods include vegetables such as kale, spinach, celery, broccoli, and some fruits such as blueberries and raspberries. It is important to note that, while these foods are low in calories, they do still contain some. So, a diet comprised mainly of vegetables will still provide your body with energy that it needs.
Takeaway
Calories remains a frequently discussed topic. It’s looked upon with dread, and many deny themselves food because they deem it “too high in calories,” no matter if it also contains beneficial nutrients. Instead of treating calories as if they are the enemy, we need to work with them by making ourselves aware of the foods we are eating, and the nutrients they provide.
One of the best ways to begin losing weight and achieving caloric balance is by replacing current calories with healthier choices. Instead of eating ice cream, eat an avocado; instead of buying pizza, making your own with healthier toppings such as chopped mushrooms, pineapple, and sweet bell peppers. By replacing empty or high calorie foods with nutrient-dense foods, you may find that you consume less calories in general because of the added bulk.
While in excess, calories can pose a serious threat to our health, they remain an essential component to our body. We are surrounded by energy, and we need it in order to survive. By focusing on your health and lifestyle choices, you can begin making changes to improve your well being and your life.